According to Canadian researchers, aspirin can increase the risk of heart attack or stroke in some patients. Although doctors have been recommending that people take aspirin daily to avoid heart problems, the researchers found that only holds true for people who are not resistant to aspirin.

However, for patients that are resistant to aspirin, taking that it becomes dangerous to their lives. Researchers say that when patients who are resistant to aspirin take the drug it makes them four times more likely to suffer a heart attack, stroke or even die from a pre-existing heart condition, according to a study published on bmj.com today.

The study was done by researchers at the University Health Network Division of Cardiovascular Surgery, Toronto General Hospital.

They reviewed all the available data on patients, aspirin and heart problems because there has been relatively little research in this are. Research is so sparse that there isn't currently an agreed on method for determining who is and isn't aspirin resistant.

But patients who have been labeled as aspirin resistant had had blood cells that are not affected by aspirin in the same way as those of patients who are responsive to aspirin, or aspirin sensitive, researchers said in a statement.

BMJ Publishing Group Ltd is a wholly owned subsidiary of the British Medical Association. Although the staff has editorial freedom, it is not a peer-reviewed journal.